Electronic devices, such as integrated circuit chips, are usually tested prior to use. Device manufacturers typically perform a number of electrical and physical tests to ensure that the devices are free from defects and that the devices function according to their specifications. Common types of device testing include burn-in testing and electrical performance testing.
The operating temperature of an electronic device under test (“DUT”) is an important test parameter that usually requires careful monitoring and/or regulating. For example, an electrical test procedure may designate a number of specific test temperatures or a specific range of test temperatures. Consequently, the prior art is replete with different types of temperature control systems, heat sink components, and heater elements designed to heat, cool, and otherwise control the operating temperature of a DUT. These temperature control systems are designed to maintain a steady state DUT operating temperature during the electronic testing procedure.
Existing heat exchangers are constructed of multiple materials, often brazed or soldered together. Although intended to produce uniform temperature control across the control surface, heat sinks with bonded layers frequently contain interstitial voids and other material discontinuities that decrease the heat removal capacity of the assemblies and decrease their uniformity. A one-directional flow through the heat sink also causes a temperature non-uniformity (rise) as the fluid transfers heat as it passes along the heater. A high thermal mass, such as is found in thick-walled heat exchangers, causes the device to respond slowly in a rapidly changing test environment.
Existing active control systems, however, rely on constant temperature, constant flow rate coolants to remove heat, which can limit the rate of temperature response and continuously draw high amounts of power.